The present invention belongs to the field of prime mover tester apparatus and methods, in general, and more particularly the present invention relates to motor vehicle automatic transmission testers.
It is common practice to test factory assembled transmissions before installation in motor vehicles. However, although it would be desirable to also test transmissions repaired in service shops and garages, and transmissions rebuilt by transmission rebuilders, test stands for testing repaired or rebuilt transmissions are not generally available in view of the high cost of such testing equipment, and more particularly of highly instrumented testing equipment of the dynamometer or brake type. Dynamometers and like apparatus are costly and delicate, often difficult to maintain in good operating condition, and they require substantially skilled personnel for proper operation, interpretation of test data, and maintenance.
Applicant has in the past developed testing equipment for prime movers, such as internal combustion engines, and automotive transmissions, as disclosed in U.S. Pat. Nos. 3,060,730, 3,505,863, and 3,592,053, utilizing the simple principle of coupling the prime mover or transmission output to a flywheel of known inertia which is driven and accelerated to a predetermined velocity. When used for testing an automatic transmission, for example, during acceleration the torque performance of the transmission output can be determined, and proper shifting of gears from low to high gear simulated as would be the case with the transmission mounted in a motor vehicle during normal acceleration in an actual road test. During deceleration, the energy stored in the flywheel is used to drive the prime mover through the transmission as would be the case in actual use on the road, such as to provide appropriate testing of the downshift operation of the transmission from high speed to complete stop.
With the recent advent of front-wheel drive motor vehicles utilizing a transaxle type of transmission, additional problems have been brought to light in view of the structural arrangement of such transaxle transmissions having an input shaft and two output shafts, each output shaft driving one of the front wheels of the motor vehicle as compared to "conventional" automatic transmissions of the type used for rear-wheel drive motor vehicles, which are provided with an input shaft and a single output shaft, generally aligned along a common centerline or having substantially parallel centerlines. Testing of transaxle transmissions by way of the inertia flywheel technique on a universal test stand requires that means be provided for aligning the input shaft of the transmission with the output shaft of a prime mover, such as an electric motor or preferably an internal combustion engine permanently mounted on the test stand, and for aligning each of the output shafts with one of the inertia flywheel shafts for coupling to the inertia flywheel shafts. Because there is a multitude of different mounts for transaxle transmissions of different makes and models, the problem of proper shaft alignment is further complicated.
The invention disclosed in co-pending application Ser. No. 493,301, now U.S. Pat. No. 4,520,659 provides a test stand for automatic transmissions, more particularly permitting alignment of the transmission input shaft and output shafts respectively with the prime mover output shaft and with the energy absorbing shafts on the test stand, in a simple and precise manner. The invention, in one of its aspects, provides a universal type of transmission testing stand capable of accepting for test straight-through transmissions as well as transaxle transmissions.
Preferably, the prime mover is an internal combustion engine which simulates more realistically than an electric motor actual conditions of operation of the transmission tested on the test stand. The transmission testing apparatus disclosed in the co-pending application comprises a pivotable bulkhead supporting the internal combustion engine having an output shaft coupled to the input shaft of the transmission. The bulkhead is pivotably supported from the base frame of the testing apparatus for alignment of the transmission output shaft with an inertia flywheel shaft while testing straight-through transmissions, and for alignment of the output shafts each with an inertia flywheel shaft when testing transaxle transmissions. More particularly when testing transaxle transmissions, positioning of the bulkhead for proper alignment may result in the internal combustion engine being disposed at an angle which may interfere with proper cooling of the engine, correct carburation and normal lubrication of the engine moving parts as a result of continuous operation at a slant angle that may hinder correct operation of constant level carburetors and unport the lubrication pump inlet line.